Pulsed windshield wiper motor control



Dec. 9, 1969 R. w. KEARNS 3,483,459

PULSE'D WINDSHIELD WIPER MOTOR CONTROL Filed March '7, 1966 6Sheets-Sheet l w gmf.

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PULSED WINDSHIELD WIPER MOTOR CONTROL Filed March 7, 1966 6 Sheets-Sheet2 INVENTOR Wlams ORNEYS Dec. 9, 1969 R. w. KEARNS 3,483,459

PULSED WINDSHIELD WIPER MOTOR CONTROL Filed March 7, 1966 6 Sheets-Sheet3 q 2- 6: MAI 794K MR 7? 0 INV ENT OR BY I A ORNEY6 Dec. 9, 1969 R. w.KEARNS 3,483,459

PULSED WINDSHIELD WIPER MOTOR CONTROL Filed March 7, 1966 6 Sheets-$heet4 INVENT OR BY 2 y A ORNEY Dec. 9, 1969 R. w. KEARNS PULSED WINDSHIELDWIPER MOTOR CONTROL 6 Sheets-Sheet 5 Filed March 7, 1966 0 w w H u M x O0 m 0 5 o II x W 00 0 0 sflwwzm Saw wmmqw INVENTOR flow M/ Keamzs AORNE'YS Dec. 9, 1969 R. w. KEARNS 3,433,459

PULSED WINDSHIELD WIPER'MOTOR CONTROL Filed March 7, 1966 6 Sheets-Sheet6 I INVENTOR fobewi /4. A e'awvza WWW United States Patent 3,483,459PULSED WINDSHIELD WIPER MOTOR CONTROL Robert W. Kearns, Detroit, Mich.,assignor, by mesne assignments, to Tann Company, Detroit, Mich., apartnership of Michigan Filed Mar. 7, 1966, Ser. No. 532,433 Int. Cl.H02p /00; H02k 27/20 US. Cl. 318310 17 Claims ABSTRACT OF THE DISCLOSUREThe present invention relates to motor control devices for controllingthe speed and operation of motors and more particularly to a controldevice for controlling the speed and operation of the motor of awindshield wiper system of a vehicle.

It is one object of the invention to provide a control device forcontrolling the speed of a motor, and particularly an electric motor, ina manner to provide improved speed torque characteristics at variousselected operating speeds.

It is another object of the invention to provide a control device forcontrolling the speed of a motor by energizing the motor intermittentlywith substantially full power pulses and to at least partially offsetthe tendency of the motor to slow down in response to increased load onthe motor by automatically increasing the percentage of ON time of eachON-OFF pulsing cycle as the motor slows down.

It is a still further object of the invention to provide a controldevice for controlling the speed of motors by pulsing the motor atsubstantially full power by a square wave ON-OFF signal generated by anoscillator sensitive to the angular position of the motor.

It is a still further object of the invention to provide a controldevice of the type described above having an oscillator sensitive to theangular position of the motor wherein the OFF time of each ON-OFFpulsing cycle is controlled independently of the position of the motorin a manner to automatically increase the ON time in response to anincrease in load on the motor.

It is a still further object of the invention to provide a controldevice of the type described above employing a plurality of rotoryswitches responsive to the angular position of the motor.

It is a still further object of the invention to provide a controldevice of the type described above wherein the aforementioned rotaryswitches are provided by a printed circuit card having a plurality ofrings thereon slidably engaged by a rotating contact assembly driven bythe motor being controlled.

It is a still further object of the invention to provide a controldevice of the type described above for energizing a windshield wipermotor of a vehicle windshield Wiper cleaning system in a manner toactivate the wiper blades intermittently through a complete wiping cyclewith a dwell period at the end of each wiping cycle.

It is a still further object of the invention to provide a controldevice for controlling a windshield wiper motor as described above toproduce intermittent operation of the wiper blades with a dwell periodat the end Patented Dec. 9, 1969 ICC of each wiping cycle. wherein thelength of time of each dwell period is automatically responsive to themoisture on the windshield, the length of time of each dwell perioddecreasing as the moisture on the windshield increases.

It is a still further object of the invention to provide a controldevice for a windshield wiper motor of the type described above whereinthe dwell period at the end of each wiping cycle is automaticallyskipped when the moisture on the windshield exceeds a threshold value toin effect place the windshield wipers in continuous operation.

It is a still further object of the invention to provide a simple andeconomical printed circuit card control device for controlling theoperation of a windshield wiper system in a manner to enable the wiperblades to be selectively operated in a continuously variable mode ofoperation, or an intermittent mode of operation having an automaticallyvariable predetermined dwell period at the end of each wiping cycle andautomatically skipping the dwell period at the end of each wiping cyclewhen the moisture on the windshield exceeds a threshold value.

It is a still further object of the invention to provide a printedcircuit card control device of the type described above which controlsone or more transistors for switching the motor ON and OFF with an RCtime constant provided for at least partially controlling the OFF timeof the transistors.

It is a still further object of the invention to provide a printedcircuit card control device responsive to the angular position of awindshield wiper motor for activating windshield wiper bladesintermittently through complete wiping cycles with a dwell period at theend of each wiping cycle.

Other objects and features of novelty of the present invention will bespecifically pointed out or will otherwise become apparent whenreferring, for a better understanding of the invention, to the followingdescription taken in conjunction with the accompanying drawings,wherein:

FIG. 1 is a perspective view of the components of a vehicle windshieldwiping system embodying features of the invention;

FIG. 2 is an enlarged view of the conductive ring face of a printedcircuit card mounted on the wiper motor unit illustrated in FIG. 1;

FIG. 3 is a fragmentary side view of the rotating wiper contact assemblyslidably engaging the conductive rings on the face of the printedcircuit card of FIG. 2;

FIG. 4 is a schematic circuit diagram illustrating one embodiment of thecontrol device of the present invention;

FIG. 5 is a schematic circuit diagram similar to FIG. 4 illustrating amodification of the invention;

FIG. 6 is a fragmentary view of the conducting ring face of a printedcircuit card illustrating another modification of the invention;

FIG. 7 is a schematic circuit diagram similar to FIG. 4 illustratinganother embodiment of the invention;

FIG. 8 is a view of the conductive ring face of the printed circuit cardemployed with the embodiment illustrated in FIG. 7;

FIG. 9 is a view similar to FIG. 1 illustrating another embodiment ofthe invention;

FIG. 10 is an enlarged end view of the control knob and indicator discof the mode switch of FIG. 9;

FIG. 11 is a graph illustrating speed-torque curves;

FIG. 12 is a view of the back face of the printed circuit card of FIG.8;

FIG. 13 is a view of the conducting ring face of a printed circuit cardillustrating another modification of the invention; and

FIG. 14 is a schematic circuit diagram illustrating a modification ofFIG. 7.

Referring to FIG. 1, a windshield wiper assembly 18 is illustrated whichembodies features of the invention. It comprises a conventional motorunit 20 having an electric motor 22 driving a speed reducing unit 24.The output shaft 26 of the speed reducing unit (not shown in FIG. 1 butschematically illustrated in FIG. 3) rotates a conventional crank armconnected to links 28 and 30 which in turn are connected to the wiperblade assemblies so as to oscillate windshield wiper blades back andforth across a windshield of a vehicle in a conventional manner. Sincethe motor unit 20 to the extent just described, is conventional, it willnot be described in greater detail.

In accordance with one embodiment of the present invention, a printedcircuit card 32, illustrated in greater detail in FIG. 2, is mounted onand spaced rearwardly from a base plate 34 of the motor unit 28. Theside of the printed circuit card facing toward the base plate 34 isprovided with nine concentric rings rl-r9 each having a plurality ofconductive segments with non-conductive segments therebetween, exceptring r5, which is a complete conductive ring. The outer ring 11 is madeup of two conductive segments rlA and rlB which combine to makesubstantially one complete ring interrupted at 36 and 38 to electricallyisolate the conductive segments from one another. The base 44) of theprinted circuit card is provided with ten terminals 42-60 which areelectrically connected to the conductive segments of the various ringsby printed circuit paths printed on the back face of the printed circuitcard.

Referring to FIG. 3, a wiper contact assembly 61 is shown comprisingthree electrically isolated wiper units 62, 64 and 66 mounted on an arm68 suitably connected to the speed reducer output shaft 26 for rotationtherewith. The wiper unit 66 has three spring contact fingers fl-f3which slidably engage rings r1r3 of the printed circuit card 32, thewiper unit 64 has four spring contact fingers f4-f7 which slidablyengage the rings r4-r7, and the wiper unit 62 has two spring contactfingers f8 and f9 which slidably engage the rings r8 and r9. Referenceis made to FIG. 9 which illustrates a wiper contact assembly 114 mountedon the arm 68 of a different type of motor unit in position to slidablyengage the face of a printed circuit card 104 in a similar manner.

Referring again to FIG. 1, a mode switch 76 is illustrated which can bemounted on the dashboard panel 78 of the automotive vehicle in positionto enable the operator to manually control the operation of thewindshield wiper blades by adjusting the following: a knob 89 fixed onthe end of a shaft 82 of the mode switch, a ring 84 keyed to a sleeve86, and a safety skip lever 88 which is keyed to a sleeve 5'0 of themode switch. With this construction, the ring 84 and safety skip lever88 separately control the sleeve 86 and sleeve 90, respectively, toperform separate control functions as will be described in greaterdetail hereinafter, and the knob 80 controls the shaft 82 which actuatesthe movable contact of a threeposition switch having five sections, aswill be described, the three positions being indicated on the face ofthe indicator disc 87 as OFF, VAR (variable speed continuous wiping) andINT (intermittent wiping).

The remaining components of the control device of the present invention,such as transistors, resistors and capacitors, are all contained withina small housing 92 having flanges 94 and 96 for mounting the housing ina suitable position, such as on the fire wall of the vehicle immediatelybehind the dashboard panel 78. An electric cable 98 having the necessarywires therein is connected to the mode switch 76 and extends therefromas illustrated to the electric motor 22, the electrical componentswithin the housing 92 and the windshield washer to provide the necessaryelectrical connections.

T he complete schematic circuit diagram of the control device of thepresent invention is illus a ed n F 4 wherein the various rings of theprinted circuit card are schematically illustrated as switches rlA, rlB,r2r8, r9A and r9B, and the five switch sections or the mode switch76.are illustrated as single-pole, three-position switches Sl-SS, eachhaving three contacts corresponding to the OFF, VAR and INT positionspreviously mentioned, the movable contact of each of the five switchsections being in the OFF position as illustrated in FIG. 4. The othermain components of the circuit are transistors Q1 and Q2 with theelectric motor 22 connected in series with the emitter-collector circuitof the transistor Q2, the capacitors C1 and C2, fixed resistors R1, R2and R3, and a variable resistor or potentiometer P1 having two wiperarms WA and WB.

Before describing the circuit of FIG. 4 in detail, the general operationof the wiper unit will be described. One of the three positions of themode switch 76 is selected by the operator by rotating the knob so thatthe pointer thereon is directed to the desired position on the indicatordisc 87. 'When the VAR position is selected, the motor 22 is pulsed in aunique manner to operate continuously at a speed determined by theposition of the wiper arm WA (FIG. 4) on the potentiometer P1, theposition of the wiper arm WA being controlled by the ring 84 of the modeswitch. The motor 22 will operate at its maximum speed when the entirepotentiometer P1 is shunted out of the circuit by the wiper arm WA, andas the wiper arm is moved upwardly along the potentiometer away from theresistor R2 to add more of it into the circuit, the full power pulseschange to decrease the percentage of time the motor is energized so thatthe speed of the motor decreases until it reaches its slowest speed whenthe entire potentiometer P1 is in the circuit. However, at high and lowspeeds, the motor is energized at substantially full power each time itis pulsed.

When the operator selects the INT position by turning the knob 80 to itsextreme clockwise position, the motor will be energized intermittentlyto actuate the wiper blades through one complete cycle across thewindshield, that is through a complete upstroke and return stroke backto a point near the park position of the wipers. At the end of thereturn stroke, the motor 22 is automatically deenergized by the controlcircuit for a predetermined dwell period, and then reenergized by thecontrol circuit to actuate the wiper blades through another completecycle followed by a dwell period. The length of the dwell period iscontrolled by the position of the wiper arm WA which is controlled bythe ring 84 of the mode switch, as previously described.

The intermittent mode of operation with the dwell period at the end ofeach cycle is of course selected during a light rain or drizzle whenthere is insufficient moisture on the windshield to require operatingthe wiper blades continuously. In accordance with a unique feature ofthe present invention, the control circuit of the present invention alsoautomatically provides a unique safety skip feature when in theintermittent mode of operation. In the event the rainfall increases soas to increase the moisture on the windshield, or in the event sprayfrom the road increases the moisture on the windshield, such as whenanother vehicle is passed, the windshield wiper blades willautomatically skip the dwell periods at the end of each cycle to ineffect automatically place the wiper blades in continuous operationuntil the moisture on the windshield again drops below a predeterminedthreshold value, at which time the wiper blades automatically return tothe intermittent mode of operation with the dwell period at the end ofeach cycle. The threshold value at which the wiper blades automaticallychange from intermittent operation to continuous operation, and viceversa, in response to the moisture on the windshield is controlled bythe position of the wiper arm WB on the potentiometer P1 which, in turn,is controlled by the safety skip lever 88. Consequently, when the operatr s e s the in ermittent mode of operation b cause of a light rainfallor drizzle, he also simply positions the safety skip lever so that thewiper blades dwell at the end of each cycle and thus, in effect, selectthe threshold value at which the safety skip feature will come intoplay. Of course, in a simplified version of the control device, thesafety skip lever 88 could be eliminated and the position of the wiperarm WB determined by an adjustment made at the factory with suitableprovision made for future infrequent adjustments to compensate for wearof the wipers or other changes in conditions. However, the safety skiplever 88 provides a very simple and desirabl way of enabling theoperator to in effect dial in the desired safety skip point at the timehe selects the intermittent mode of operation.

The operation of the control circuit illustrated in FIG. 4 will now hediscussed in detail. The emitter of the transistor Q2 is connecteddirectly to ground with the collec' tor thereof connected to one side ofthe armature of the motor 22 which in this embodiment is a DC motorhaving a constant field. The constant field can come from a permanentmagnet or a wound field supplied by a constant voltage. The wound fieldcould be a shunt, compound or other type of winding. The other side ofthe motor armature is connected to the movable contact of switch S4which, as previously described, forms one section of the mode switch 76.The emitter of the transistor Q1 is connected to the base of thetransistor Q2 and to ground through a temperature compensating resistorR3. The collector of the transistor Q1 is connected to the collector ofthe transistor Q2 and to the OFF contacts of the switches S3 and S4throguh the ring r7 of the printed circuit card.

When the mode switch is turned to the VAR or continuously variableposition, the switch S4 connects the motor 22 to a negative source ofvoltage B, such as the negative terminal of a vehicle battery, and thebase of the transistor Q1 is also connected to the negative potential Bthrough the capacitor C1 and the resistor R1 when the switches formed bythe conductive segments rlB and rlA (both of which are connected to thenegative terminal of the capacitor C1) and the ring r2 are closed. Thering r3 also is employed as will be described and is connected to groundthrough the switch S5. The rings r4, r5, r6, r7, 1'8 and conductivesegments r9A and r9'B are not used electrically in the continuouslyvariable mode now being described. The wiper arm WA is connected to thenegative potential B through the switch S3 and the wiper arm WB iselectrically disconnected from the circuit by the switch S2. Should thewiper contact assembly 61 stop in the gap between rings r1A and rlB whenturned off after a previous use, the motor would start up becausecurrent flows out of the base of the transistor Q1 through resistor R2,potentiometer P1, the

wiper arm WA and switch S3 to the negative potential B. Because of this,the conductive segments rlA and rlB may be considered, in the variablemode of operation, as forming one complete ring r1 which cooperates withrings r2 and r3 and the rotating wiper contact assembly 61 to form atwo-pole, single-throw switch which op crates as many times perrevolution of the wiper contact assembly as there are conductivesegments on the rings r2 and r3. For the card shown, ring r1 isconnected to the conductive segments of the ring r2 and then to theconductive segments of the ring r3 and back to the conductive segmentsof the ring r2 at the rate of 60 times per revolution of the wipercontact assembly if the 0 angle pattern were the same as the rest of thecard.

It is important to note that this switching function serves as a squarewave oscillator for pulsing the motor 22 which is sensitive to bothposition and the load torque on the motor.

Continuously variable mode of operation The variable mode of operationwill be discussed first, with the assumption that the load torque isconstant. When the wiper contact assembly is positioned so that the ringr1 is not connetced to a conductive segment on either r2 or r3, themotor 22 is turned ON by the base current flowing through resistor R2and potentiometer P1. Since the motor is ON, the wiper contact assemblycontinues to turn until ring 11 is connected to a conductive segment onring r2. The motor is still ON, but even more so now since base currentflows into capacitor C1 as well as flowing through resistor R2 andpotentiometer P1. The current flowing into capacitor C1 charges it, andthere is ample time for the capacitor to become fully charged since itis a small capacitor. The negative terminal of the capacitor is now at Bpotential with the positive terminal at about 0.4 volt due to thevoltage drop across the transistor emitters. As the motor continues toturn the wiper contact unit 66, ring r1 is disconnected from aconductive segment on ring r2, but the capacitor C1 retains its chargeand again the motor stays ON due to current flowing through resistor R2and potentiometer P1. As the motor continues to turn the wiper contactunit 66, ring 11 is connected to a conductive segment on ring r3.However, since the voltage drop across the capacitor C1 cannot changeinstantaneously, the positive terminal of the capacitor is at -{-B voltspotential because the negative terminal of the capaictor is nowconnected directly to ground.

With the base of the transistor Q1 positive with respect to its emitter,the transistors are turned OFF to turn the power to the motor 22 OFF.The motor, however, will continue to turn due to the momentum of thewindshield wiper system. The capacitor C1 discharges through theresistor R2 and potentiometer P1 toward B volts. Therefore, the basepotential of the transistor Q1, which has been at +B volts dischargeswith a short RC time constant toward B volts. The time that the motor 22is OFF depends upon how long the base is positive with respect to theemitter which in turn depends upon the setting of the potentiometer P1which varies the RC time constant. When the base voltage of thetransistor Q1 returns to approximately 0.4 volt, the transistors areturned ON and the motor 22 again receives power even though the ring r1may still be connected to the ring r3 by virtue of the wiper contactunit 66 still contacting a portion of a conductive segment on ring r3.Capacitor C1 is practically discharged and the transistors are ON byvirtue of base current flowing through the resistor R2 and potentiometerP1. The motor remains ON while the wiper contact unit 66 leaves theconductive segment on ring r3 and recharges the capacitor C1 byconnecting ring r1 to a conductive segment on ring r2, as previouslyexplained. The motor is turned OFF as soon as the wiper contact unit '66contacts the leading edge of the next conductive segment on ring r3.Thus the motor is rapidly pulsed at full power during the continuouslyvariable mode of operation, but the windshield wiper blades operatesmoothly and the system seeks out an equilibrium speed where the powerinput just balances the system losses and the Work done.

When the capacitor C1 discharges quickly due to a low value of thepotentiometer P1 (as determined by the position of the wiper arm WAcontrolled by the ring 84 on the mode switch 76), the motor is ON alarger percentage of the time and the motor speed is therefore fast.Furthermore, the motor is energized at substantially full power eachtime it is turned ON because the emitter-collector circuit of thetransistor Q2 dissipates very little power as compared to the variableresistors commonly connected in series with a motor to vary its speed. Aminimum value of speed is established by the ratio of (l) the width ofthe space between the narrower conductive segments on the ring r3positioned outside the angle 0 on the printed circuit card and (2) thecombined width of such a space and the width of one narrower conductivesegments. It will be apparent that this is the case because even if thebase voltage of the transistor Q1 has not decayed to O.4 volt, the motor22 turns ON when the wiper unit 66 leaves a conductive segment on thering r3 since the negative terminal of the capacitor C1 is electricallydisconnected from ground and base current flows through resistor R2 andpotentiometer P1.

It will be observed that in the region of the printed circuit cardindicated by the angle 0, hereinafter referred to as the 9 region, thewidth of the conductive segments on the rings r3 and r2 changes, withthe conductive segments at the beginning of the angle being wider thanthe conductive segments near the end of the angle 0. Specifically, inthe angle 0 there are five conductive segments on the ring r3 and fouron the ring r2. This is of primary significance in connection with theintermittent mode of operation to be described since for thecontinuously variable mode now being described, the number of conductivesegments in the 0 region is not too important. The principal effect ofthese particular segments is that the motor is ON for a greatlyincreased percentage of time due to the elongated segments on the ringr3 in the 0 region so that the motor speed picks up in this region,which is symmetrical with respect to the park position of the wiperblades, to provide a quick turnaround feature. At this point it is notedthat the speed of the wiper assembly relative to the printed circuitcard is constant assuming the speed of the motor 22 is constant, whereasthe speed of the wiper blades during one complete cycle more or lessfollows a sine wave so that at the turnaround points of the wiper bladesthe blades are travelling slower relative to the speed of the motor thanthey are at the mid-points of the upstroke and return stroke. By varyingthe conductive segment pattern on the rings 12 and r3, it is apparentthat a variety of wiper blade speeds versus wiper blade positions can beachieved.

By pulsing the motor with substantially full power pulses thespeed-torque characteristics of the motor are greatly improved. Thiswill be apreciated by considering the effect of an increase in load onthe wiper motor 22 due to increased drag encountered by the wiper bladeson the windshield, for example. The RC time constant previouslydescribed depends on time and is independent of the load, whereas anincrease in load slows the motor 22 down. Therefore, it takes a longertime for the wiper unit 66 to reach the end of a conductive segment onthe ring 16, at which point the transistors are automatically turned ONif the base voltage has not decayed to O.4 volt as previously described.However, since the RC time constant is fixed for a given position of thewiper arm WA, the base voltage will decay to this value after a giventime and the transistors will be turned ON even though the wiper unit 66is still on a conductive segment on the ring r3 due to the reduced speedof the motor 22. Thus the percentage of ON time in each ON-OFF cycle ofthe pulsed operation is au omatically increased to partially offset theincrease in load. Stated otherwise, during the continuously variablemode of operation, the motor is pulsed on and off by the switchingfunction provided by rings r1-r3 which serve as a square wave oscillatorsensitive to both position and load torque, as previously mentioned. TheOFF time begins when the wiper unit 66 engages a conductive segment onthe ring r3 and ends as soon as either of the following events takesplace: (1) the base voltage of the transistor Q1 decays to O.4 volt asdetermined by the RC time constant or (2) the wiper unit 66 breaks itselectrical connection with the conductive segment on the ring r3. Sincethe RC time constant is' fixed for a given position of the Wiper arm WA,as mentioned previously, the OFF time can never exceed this amount oftime. Therefore, as the time for each complete cycle of the switchrepresented by rings r1r3 increases in length due to the motor slowingdown in response to an increased load (that is the frequency of thecycles decreases), the percentage of time that the motor is ON relativeto the time that it is OFF will increase.

This increase in full power ON time results in improved speed torquecurves such that when the speed of the motor at high, medium and lowspeed settings is plotted versus the torque on the motor, with speed asthe ordinate and torque as the abscissa, the resulting three curves eachapproach the desired horizontal lines. At each speed setting, the speeddecreases only a small amount as the load on the motor increases. Thisis a big improvement over the conven ional motor control having thevariable resistor in series with the motor wherein the motor speed atlower speed settings drops off drastically as the load on the motorincreases.

Of course, it will be appreciated that although the continuouslyvariable, pulsed mode of operation has been described in connection withcontrolling a windshield wiper system, and is particularly useful insuch a system, it can be used for "controlling the speed of motors ingeneral to provide the same improved speed torque characteristics forthe motor. Further, although the printed circuit card and wiper assemblyprovide an excellent simplified manner for producing square waveoscillations for pulsing the motor wherein the percentage of ON time ofeach pulsing cycle increases as the load on the motor increases anddecreases as the load on the motor decreases, other apparatus could beused for generating the square wave oscillations responsive to theangular position of the motor to provide substantially the samevariation of ON time percentage.

Intermittent mode of operation When the mode switch 76 is placed in theINT (intermiLtent) position by moving the knob 80 to its' extremeclockwise position, the movable contact of each of the switches Sl-SSengages the extreme clockwise contacts of each switch. In this positionwherein the wiper blades operate intermittently, the circuit is exactlythe same as when in the continuously variable position previouslydescribed except that a larger capacitor C2 is connected to the base ofthe transistor Q1 when the conductive segment r1A is engaged by thewiper contact unit 66 to provide a larger time constant for the dwellperiod at the end of a wiping cycle, as will be described. The capacitorC1 is electrically connected to the base of the transistor Q1 butfunctions only when the conductive segment rlB is engaged by the wipercontact unit 66. In the intermittent mode of operation, each wipingcycle of the windshield wipers is divided into three regions; fulltorque, controlled torque and the 0 region which, as previously mentioned, is centered about the park position of the wiper blades. Thefull torque region corresponds to the portion of the upstroke of thewiper blades beginning with the end of the 0 region and terminating atthe gap 38 between the conductive segments HA and rlB which, in thisembodiment, is located at the turnaround point at the end of theupstroke but could be located elsewhere to change the length of the fulltorque region. Therefore, on 'the printed circuit card 32, the gap 38 isdiametrically opposite the middle of the 0 region, and the controlledtorque region corresponds with the portion of the downstroke from itsbeginning of the 0 region.

It is desirable to have full torque on the upstroke of the windshieldwiper blades to remove any obstacles or for iced in blades. In this fulltorqe region the motor 22 is connected directly to ground through rings26 and r5 to electrically remove the transistors from the circuit. Ringr5 is connected directly to ground through the extreme clockwise contactof switch S5 and ring 16 is connected directly between the transistor Q2and motor 22. Since the conductive segment of the ring 16 is coextensivewith the full torque region, the wiper contact unit 64 will complete thecircuit between these rings, and therefore connect the motor 22 directlyto ground to remove the transistors from the circuit during the fulltorque region, and the transistors will be automatically electricallyconnected back into the circuit as soon as the wiper contact unit 64leaves the conductive segment of the ring r6.

During the controlled torque region at the beginning of the downstroke,the input power to the motor is controlled as in the continuouslyvariable mode through the conductive segment rlB and capacitor C1 topulse the motor, as previously described. However, it will be noted thatthe speed of the motor in the controlled torque region will depend uponthe position of the wiper arm WB on the potentiometer P1 which isconnected to the negative potential B through the conductive segment r9Bof the ring r9 which lies in the controlled torque region, the positionof the wiper arm WB being controlled by the safety skip lever 88(FIG. 1) as previously explained. The wiper arm WA on the potentiometerP1 is electrically connected in the circuit only during the region bythe conductivesegment r9A which is coextensive with the 6 region.

Controlling the speed of the motor 22 by means of the safety skip lever88 during the controlled torque region serves to control the kineticenergy of the windshield wiper system as it enters the 6 region. At thebeginning of the 0 region, the transistors are turned OFF and the wiperblades coast until the work done by the blades against the windshieldbrings them to rest (in a light rain) somewhere in the 0 region,depending upon the kinetic energy of the system as it enters the 0region and the moisture on the windshield Which determines the drag ofthe blades against the glass. The wiper blades will come to rest in oneof the five conductive segments on the ring r3 in the 0 region and willdwell for a period of time determined by the position of the wiper armWA on the potentiometer P1, which again is controlled by the ring 84 ofthe mode switch. This arrangement senses the moisture on the windshieldand produces a dwell period which increases in time when the moisture onthe windshield decreases, and decreases in time when the moisture on thewindshield increases.

When the capacitor C2 is connected to ground through the switch S1,conductive segment rllA and ring r3, it immediately makes the base ofthe transistor Q1 positive and turns the transistors (and motor 22) OFFuntil the capacitor discharges sutficiently through the resistor R2 andpotentiometer P1 so that the voltage on the base of the transistor Q1decays to about 0.4 volt. The transistors then turn back ON asperviously described and energize the motor 22.

When in the intermittent mode of operation, the ring r3 is not tieddirectly to ground as it was in the continuously variable mode ofoperation. The contact fingers contacting rings r4, r5, rd and r7 areshorted together since they form part of the same wiper contact unit 64.Since the ring r is now connected to ground through switch S5 and theconductive segment of ring r4 is a physical extension of the conductivesegments of ring r3, ring r3 is connected to ground during thecontrolled torqueand 0 regions and is electrically disconnected from thecircuit during the full torque region. When the wiper contact unit 62 ison the conductive segment r9A, the negative potential B is connected topotentiometer P1 through the wiper arm WA so that the position of thewiper arm WA controls the dwell time. When the wiper contact unit 62 ison the conductive segment r9B, the negative potential -B is connected tothe potentiometer P1 through the wiper arm WB so that the position ofthe wiper arm WB determines the speed of the motor in the controlledtorque region, and therefore the kinetic energy of the system as itenters the 0 region, as will be described in greater detail hereinafter.It will be noted that the conductive segment rllB is substantiallycoextensive with the conductive segment r9B and that the segment rlBoverlaps slightly into the 6 region. This overlap does no harm andprovides additional tolerance on wiper position.

During the full torque region, the ring 3 is an open circuit. Althoughthe two-pole, single-throw switch in effect provided by rings r1, r2, r3and rotating wiper contact unit 62 operates mechanically, only theconductive segment rlA and ring r2 are used electrically. When theconductive segment rllA is connected to ring r2 during the full torqueregion, the capacitor C2 is charged. At the end of the full torqueregion, capacitor C2 is fully charged and is electrically disconnectedfrom the circuit with the charge retained until later.

At the beginning of the controlled torque region, ring r3 is connectedto ground through rings 14 and r5. The circuit uses capacitor C1 bymeans of conductive segment rlB to operate in the continuously variablemode previously described. The potentiometer P1 is connected in thecircuit through wiper arm WB (the sensitivity control) by the conductivesegment r9B. Thus, all the components required for the continuouslyvariable mode of operation are in the circuit during the controlledtorque region and the control operates in the continuously variable modeuntil the wiper contact assembly 61 leaves the controlled torque regionand enters the 0 region.

At the end of the controlled torque region, the conductive segment rlAis engaged by the Wiper contact assembly to connect the fully chargedcapacitor C2 back into the circuit, while the conductive segment r9A isengaged to connect the potentiometer P1 in the circuit through the wiperarm WA so that the control circuit operates in its intermittent mode, asdescribed previously. After the control either times out (or skips thedwell period, as will be described), the capacitor C2 is again chargedin the full torque region and the cycle repeats.

If the ring r3 in the 9 region were one solid conductive segment ratherthan being divided into five conductive segments as illustrated, themotor 22 would drive the wiper blades out of the 6 region into the fulltorque region wherein the rings r6 and r5 remove the transistors fromthe circuit and connect the motor 22 directly to ground as perviouslydescribed. Consequently, the dwell time at the end of each wiping cyclewould depend solely on the RC time constant provided by the capacitor C2and the resistor R2 and potentiometer P1. Since dwell times up tofifteent or twetnty seconds may be desired, the capacitor C2 would haveto be quite large. However, when the ring r3 is divided into fiveconductive segments in the 0 region as illustrated in FIG. 2, the motor22 will be energized after the RC time constant times out until thewiper unit 66 reaches the beginning of the next conductive segment onring r3, at which point the motor will be deenergized for another dwellperiod, the wiper contact unit 66 having passed over a conductivesegment on the ring r2 in the gap between the conductive segments onring r3 to recharge the capacitor C2 before the motor stops. When thewiper contact unit 66 stops on the next conductive segment on the ringr3, as just describetd, the conductive segment rlA will be connected toground through the ring r3 to cause the base of the transistor Q1 to gopositive as a ready described to deenergize the motor 22 for anotherdwell period controlled by the RC time constant.

This operation repeats itself until the motor 22 steps the wiper contactassembly out of the 0 region into the full torque region. Thus the totaldwell time at the end of a wiping cycle depends on the number of stopsthe wiper blades make in the 0 region multiplied by the time requiredfor the RC time constant to time out during each stop. Therefore, asmaller capacitor (still larger than capacitor C1) can be employed toprovide the aforementioned fifteen to twenty second dwell periods, ifdwell periods of this length of time are desired. Further, if the bladesstop so that the wiper contact unit 66 is on the first conductivesegment on ring r3, a maximum dwell period will be provided, and if thewiper blades coast further after the motor 22 is deenergized at thebeginning of the 6 region so that the wiper contact unit 66 stops on thelast and shortest conductive segment on ring r3, a minimum dwell periodwill be provided. It is apparent that this is exactly what is desired.The more moisture on the windshield, the further the wiper blades willcoast into the region so as to require fewer steps for the wiper bladesto get out of the 0 region. Therefore, the total dwell time at the endof such a wiping cycle will be relatively short, and the frequency ofwiping strokes will be correspondingly higher to keep the windshieldclear. On the other hand, when the moisture on the windshield decreases,as it will when the rainfall decreases, the wiper blades will coast to astop earlier in the 0 region, and thus provide a longer dwell period atthe end of each wiping cycle. In this manner, the control device of thepresent invention is automatically sensitive to the amount of moistureon the windshield to provide a longer dwell period when the moisture islow so as to require a lower frequency of wiping strokes to keep thewindshield clear, and a shorter dwell period when the moisture increasesso as to require a higher frequency of wiping strokes to keep thewindshield clear.

Safety skip feature This leads to still another unique feature of thecontrol device of the present invention. While in the intermittent modeof operation as just described, the rainfall may become heavy, or sprayfrom traffic may significantly increase the moisture on the windshield.Under these and similar conditions, it is safer if the Wiper bladesoperate continuously rather than in the intermittent mode with the dwellperiod at the end of each wiping cycle. The control device of thepresent invention automatically changes to a safety skip mode ofoperation when the amount of moisture on the windshield exceeds athreshold value wherein the dwell period is skipped at the end of eachwiping cycle so as, in effect, to place the wiper blades in continuousoperation. Since the friction of the wiper blades on the windshieldvaries with the amount of moisture on the windshield (the frictiondecreasing as the moisture increases) when the amount of moisture on thewindshield reaches the threshold value, the wiper blades will coastthrough the 0 region and enter the full torque region without coming toa stop. Consequently, the motor 22 will be energized as soon as the fulltorque region is entered to skip the dwell period and start anothercycle. The capacitor C2 is recharged during the full torque region, andthe system prepares to make the decision as to whether or not it willdwell at the end of the return stroke. The dwell periods will continueto be skipped as long as the moisture is above the threshold value andthus, in effect, provide continuous operation. When the moisture on thewindshield drops below the threshold value, the wiper blades will againcoast to a stop and dwell in the 0 region as previously described andresume intermittent operation.

Essentially, if the work done by the wiper blades in the 0 or coastregion is equal to the kinetic energy of the system, the wiper bladeswill stop and the control will time out. If the work done is less thanthe kinetic energy of the system, the blades will not stop and the dwellperiod will be skipped. The amount of energy removed from the system bythe blades moving across the windshield in the 0 or coast region isgreatly affected by the moisture on the windshield. Variations inkinetic energy also can occur from vehicle to vehicle due to Variationsin battery voltage and losses in the system, and also from changes inthe condition of the rubber of the wiper blades. Personal preference ofthe operator can also dictate how much moisture is on the glass at thetime the safety skip occurs. For these reasons, a sensitivity control isprovided which can be controlled by the vehicle operator by adjustingthe safety skip lever 88 to vary the position of the wiper arm WB on thepotentiometer P1 and thus control the speed of the motor in thecontrolled torque region.

Basically, the safety skip lever 88 allows the pulsed input power to themotor to be controlled as previously described so that it the driverprefers more moisture to be present on the windshield before the wiperblades skip the dwell period, he can adjust the lever so that the pulsedinput power to the motor 22 is reduced. Obviously, with less kineticenergy at the beginning of the 6 region, more moisture (and thus lessfriction) is required before the wiper blades will skip the dwellPeriod. If desired, however, the wiper arm WB can be connected to thenegative voltage -B through the conductive segment r9B which iscoextensive with the controlled torque region and the position of thewiper arm WB adjusted at the factory and, thereafter, infrequentlyadjusted by a mechanic or the like rather than being controlled by thesafety skip lever 88. However, the safety skip lever 88 provides a verysimple and desirable control to enable the operator to dial in thedesired safety skip point at the time he selects the intermittent modeof operation.

Capacitor C1 is used during the controlled torque region of the cyclewhile the larger capacitor C2 is used in the 0 region to provide thedwell time. Since the capacitors C1 and C2 are used in differentportions of the cycle, only one potentiometer P1 is required along withthe two wipers WA and WB to provide the individual adjustments. Themotor 22 receives a pulse of power through the conductive segments onring r2 in the 0 region before it reaches the beginning of eachsub-region defined by the beginning of the conductive segments on thering r3, this burst of power occurring so that the capacitor C2 can berecharged between sub-regions. The varying angularlengths allotted tothe conductive segments on ring 12 in the 0 region for charging thecapacitor C2 result in varying the dwell time associated with eachsub-region. This refinement can lead to further economies in the controlunit. The maximum dwell time in a single step model (one sub-region orconductive segment on the ring r3 in place of the five illustrated)depends solely upon the RC time constant involved, as previouslymentioned. The maximum value of the resistance employed (resistor R2plus potentiometer P1), depends upon the transistor gain. The higher thevalue of the resistance, the more the transistor gain required. Thelower the value of the resistance, the less transistor gain required.However, the maximum time in a multiple (n) step model (such as the fivesub-region model illustrated) can be (n) times that of a single stepmodel for the same RC time constant, as already explained. Thus, toachieve the same maximum dwell time, the value of the resistance(resistor R2 plus potentiometer P1) also can be decreased by a factor of(n) which, in turn, enables the transistor gain required also to bereduced by a factor of (n). If desired, a sufiicient number ofsub-regions can be employed in the 0 region so as to require only onetransistor rather than the two illustrated in FIG. 4.

Further, since the dwell time is automatically adjusted in response tothe moisture on the windshield, the potentiometer and wiper arm WA forproviding dwell time adjustment can be eliminated, if desired. It isclear that discrete values of safety skip sensitivity adjustment wouldalso be satisfactory. If there are (n) safety skip sensitivityadjustments, there can be (n) distinct fixed speeds when operating inthe continuous mode, rather than an infinitely variable number of speedsas previously described. The economical circuit based on theseprinciples and yet containing all of the refinements of the circuit ofFIG. 4 is shown in FIG. 5.

Referring specifically to FIG. 5, it will be noted that the controlcircuit illustrated is similar to the control circuit of FIG. 4 with thefollowing exceptions. The transistor Q2 is eliminated and thepotentiometer P1 replaced by a plurality of series connected resistorsR3- R8. Suitable tap points are provided between and at the ends of theseries connected resistors R3-R8 for cooperating with wiper arms WA andWB to vary the total resistance in the circuit by discrete increments.Although five resistors with six tap points are illustrated,

it is apparent that this number can be increased or decreased ifdesired. The wiper arm WB is connected to the INT contact of the switchS2 and the wiper arm WA is connected to the movable contact of theswitch S2. The movable contact of the switch S2 is connected to thesource of negative potential B through the conductive segment r9B on thering 19. The switch S3 is connected as before with the exception thatthe movable contact thereof is connected to the end of the resistor R8for a purpose to be described.

In the continuously variable mode of operation, the control circuitfunctions in the same manner as previously described with its speeddetermined by the position of the wiper arm WA which controls theresistance of the RC time constant including the capacitor. The primarydifference is that movement of the wiper arm WA from one tap to anotherdiscretely varies the resistance whereas in the control circuit of FIG.4 the resistance of the potentiometer is infinitely variable. However,it is apparent that a small number of the resistors R3-R8 provide anadequate speed adjustment as a practical matter.

By connecting both the wiper arm WA and the resistor R8 to the movablecontact of the switch S3, base current can flow in the transistor Q1while the wiper arm is being shifted from one tap point to another. Ifthis end of the resistor R8 were not electrically connected to anything,such as is the case with the upper end of the potentiometer P1 of FIG.4, the transistor Q1 would be turned OFF to deenergize the motor 22while the wiper arm WA is being shifted except possibly for the briefpulses that would occur when the capacitor C1 is being charged throughring r2.

In the intermittent mode of operation, the wiper arm WA is electricallyconnected in the circuit by the conductive segment r9A during theregion, and the wiper arm WB is electrically connected in the circuit bythe conductive segment r9B during the controlled torque region.Therefore, the wiper arm WB can be adjusted to control the speed of themotor in the controlled torque region by controlling the number ofresistors R4-R8 connected in the circuit between the positive terminalof the capacitor C1 and the source of negative potential B, and thewiper arm WA can be adjusted to control the time constant during thedwell period in the 0 region.

Modified depressed park During the intermittent mode of operation, theposition of the wiper blades during the dwell period varies within the 0region in response to the moisture on the windshield, as .previouslydescribed, but when the mode switch 76 is turned to the OFF position,the wiper blades are accurately stopped at the bottom of the returnstroke by the short conductive segment on ring r7. Referringspecifically to FIG. 4, it will be observed that the circuit in the OFFposition is exactly the same as in the intermittent position of the modeswitch 76 except that, in addition, rings r7 and r8 are used. When thecontrol is in the OFF mode, power is supplied to the circuit throughring r8 so that the wiper blades will complete an intermittent modecycle. On a moist windshield, the wiper blades will stop at the end ofthe wiping cycle, the control will time out, and the motor 22 will startup again. During the start-up, the kinetic energy is low and the ring r8becomes open-circuited to remove power from the motor just before thebottom of the return stroke. When the wiper contact unit 64 of the wipercontact assembly engages the short conductive segment on the ring r7,the armature of the deenergized motor is short-circuited so that theremaining kinetic energy of the system is dissipated in electrodynamicbraking to brake the wiper blades to an abrupt stop within theconductive segment on the ring r7.

On a wetter windshield, the wiper blades will coast further into the 0region and therefore the system will still possess some kinetic energywhen the wiper contact unit 64 reaches the short conductive segment onring r7. When coasting, the motor is deenergized by the transistors, andagain the motor is disconnected from the negative potential B when thering r8 open circuits. The dynamic braking action is thereafter providedby the conductive segment on the ring r7 and is still capable ofstopping the wiper blades within the short conductive segment becausethe system has lost energy while traversing the preceding portion of the0 region. It is the loss of energy in the 0 region or the fact that themotor is just starting up after a dwell period which enables theconductive segment on ring r7 to be short so as to provide a closeposition control of the OFF position of the wiper blades. The controlcircuit illustrated in FIG. 5 functions in a similar manner when themode switch 76 is moved to the OFF position to complete an intermittentcycle of operation and bring the blades to final rest when they reachthe conductive segment on the ring r7.

Referring to FIG. 6-, a fragmentary portion of a printed circuit card102 at the end of the 0 region is shown to illustrate a modification ofthe invention. In this printed circuit card 102, the 0 region liesentirely within the return stroke of the wiping cycle, rather than beingpartially in the return stroke and partially in the upstroke as is thecase of the printed circuit card 32 illustrated in FIG. 2,

and the upstroke of the next wiping cycle begins at the.

end of the 0 region. The conductive segment on the ring r7 lies entirelywithin the upstroke. The ring r5 is at ground potential, as can be seenby referring to FIG. 4, and since the wiper contact unit 64 associatedwith the rings r4, r5, r6 and r7 electrically interconnects these rings,then the ring 16 is also at ground potential. Therefore, the collectorof the transistor Q2 is connected to ground the entire length of theconductive segment r6 which on the card 102 is coextensive with theentire upstroke of the wiping cycle so that the full torque region iscoextensive with the entire upstroke. This applies full power to themotor 22 with the transistors removed from the circuit during the entireupstroke.

This provides an important advantage in that when the wiper blades arelocated anywhere within the conductive segment on the ring r7 (as theywill be when the system is turned OFF) and the mode switch 76 is turnedON for a subsequent operation, the transistors will be removed from thecircuit because the wiper blades are in the full torque region whereinthe collector of the transistor Q2 is grounded through ring r6.Consequently, full power is immediately provided and if the blades arenot able to move when turned ON, such as when they are frozen in placein the winter time, the motor 22 will be the only component subjected tostall torque conditions. The motor, of course, is designed to take stalltorque conditions for about ten minutes or so until a bimetal contactopens, and therefore will not be damaged if the wiper blades cannot bemoved.

Further, in the OFF position of the mode switch, the wiper blades willstop within the conductive segment on the ring r7 of the card 102 aspreviously described, because the ring r8 positively deenergizes themotor by disconnecting the side of the motor connected to the switch S4from the negative potential B. Since the 0 region lies entirely withinthe return stroke of the wiping cycle, the wiper blades when operatingon a wet windshield must traverse the entire 0 region before reachingthe conductive segment on the ring r7 so as to lose more energy than inthe case of the printed circuit card 32 previously described.

The printed circuit card 32 of FIG. 2 could be employed with one longconductive segment on the ring r3 in the 0 region in place of the fiveconductive segments (or sub-regions) illustrated to provide what mightbe termed a single stop control device. The dwell time of such a controldevice would be established by the position of the wiper arm WA on thepotentiometer P1. By mounting the resistance element of thepotentiometer on the printed circuit card in the 0 region and mountingthe wiper arm WA on the arm 68 (FIG. 3) which rotates the wiper contactassembly, the position where the motor stops in the region willautomatically determine the resistance of the RC time constant, andhence determine the dwell time. When the wiper blades stop early in the0 region in response to a drier windshield, the potentiometer resistanceon the printed circuit card would be great and the dwell time would belong. When the wiper blades stop just short of the end of the 0 regionin response to a wetter windshield, the potentiometer resistance wouldbe low and the dwell time would be short. In both cases, this is thedesired result, and accordingly this technique would provide anautomatically variable moisture sensitive dwell period.

Further, since the potentiometer can be approximated by a group ofseries connected resistors with tap points, the tap points can beconnected to conductive segments on a ring of the printed circuit cardin the 0 region so that the plurality of segments (n) make up the 0region. When the wiper contact assembly stops on any particular segment,the time delay will be determined by the amount of resistance remainingin the 0 region. Such a group of segments is shown in the controlcircuit of FIG. 7 and the printed circuit card 104 illustrated in FIG. 8which is used with this embodiment.

Referring to FIG. 8, the printed circuit card 104 is provided with anadditional ring r0 having a plurality of conductive segments r0A, r0B,r0C, 10D, 10E and r0F adjacent thereto in the 0 region which areelectrically connected to separate terminals on one face of the base 40of the card are electrically connected to the rings r0r9B as illustratedin FIG. 12 to enable the card to be inserted in a card connector 106 asillustrated in FIG. 10.

Referring to FIG. 9, a windshield wiper assembly 108 is shown whichillustrates another embodiment of the invention. It comprises anotherconventional type of motor unit 110 having an electrical motor 112drivingly connected to a large gear 114 in a speed reducer housing 116.The gear 114 rotates an output shaft 106 which in turn rotates aconventional crank arm (not shown) connected to the links 28 and 30which actuate the wiper blade assemblies (not shown) for oscillating thewiper blades back and forth across the windshield as previouslydescribed. A wiper contact assembly 118' is mounted on the inner end ofthe output shaft 106 by an arm 119 as previously described. It has fourelectrically isolated wiper contact units 120-126 which have one, three,four and two spring contact fingers, respectively, which slidably engagethe rings r0-r9, respectively, as best seen in FIG. 8. A suitable coverplate (not shown) is bolted to the speed reducer housing 116 to enclosethe gear 114. The printed circuit card 104 is mounted within the housingin position to be slidably engaged by the wiper contact assembly 118with the base 40 projecting from the housing 116 to facilitateconnection to the card connector 106.

The transistors, capacitors and resistors of the control circuitillustrated in FIG. 7 are contained in an electrical unit 128 which iselectrically connected to the motor unit 110, the card connector 106 anda mode switch 130 mounted on the dashboard 132 of the vehicle. The modeswitch 130 has a single control knob 134 for controlling each of thefive switch sections 81-85 of the mode switch and for controlling thesingle wiper arm WA of the potentiometer P1 as shown in FIG. 7. Thecontrol knob 134 has a pointer 136 thereon which cooperates with anindicator disc 138 to indicate the position of the knob as most clearlyillustrated in FIG. 9. When the pointer 136 points directly upwardly tothe OFF position, each of the switch sections S1S5 is positioned in theOFF position as illustrated in FIG. 7, and the wiper arm WA ispositioned at the midpoint of the potentiometer P1 as shown. When thecontrol knob 134 is turned in a clockwise direction, the switch sections81-85 are immediately actuated to their extreme clockwise contacts toplace the circuit in the intermittent mode of operation, and as thecontrol knob 134 is rotated further in a clockwise direction, the wiperarm WA moves up the potentiometer P1 to increase the potentiometerresistance in series with the resistor R2. This increases the time forthe capacitor C1 to discharge which increases the percentage of OFF timeof the transistors in the controlled torque region of the wiping cycleto decrease the speed of the wiper blades. As previously described,controlling the speed of the wiper blades in the controlled torqueregion controls the skip sensitivity of the wiper blades. Therefore theoperator can simply rotate the control knob 134 to the right to selectthe skip point sensitivity suitable for the condition of the windshieldat the time he selects the intermittent mode of operation. .1

When the operator turns the control knob 134.in a counterclockwisedirection from the OFF position as illustrated in FIG. 9, each of theswitch sections 81-55 is immediately actuated to their middle contact toplace the control circuit in the continuous mode of operation. As thecontrol knob is turned further to the left in a counterclockwisedirection, the wiper arm WA moves down the potentiometer P1 from themidpoint to increase the percentage of ON time of each pulse to increasethe speed of the motor.

Referring to FIG. 8 again, the ring 13 of the printed circuit card 104has one elongated conductive segment in the 0 region which liescompletely within the return stroke of the wiping cycle and ends at thebottom of the return stroke of the wiping cycle. The short conductivesegment on the ring r7 lies completely within the upstroke as describedin connection with FIG. 6. The conductive segment on the ring 19A iscoextensive with the 0 region and may extend slightly into the fulltorque region since this does no harm and provides additional tolerancecontrol. The conductive segment r9B is coextensive with the controlledtorque region and also may extend into the full torque region sinceagain this does not affect the operation. The conductive segment rlAextends from the gap 36 at the beginning of the 0 region to the gap 38at the end of the upstroke and the conductive segment rlB is coextensivewith the controlled torque region. The ring r6 determines the fulltorque region which, in this embodiment, is coextensive with the entireupstroke of the wiping cycle. The ring r4 is coextensive with the entirereturn stroke of the wiping cycle which, in this embodi ment, comprisesthe controlled torque region and the 0 region. The ring r8 isinterrupted by a single gap longer than the length of the conductivesegment on the ring r7 and the ring 15 is a complete ring, as before inthe embodiment of FIG. 2.

Referring to FIG. 7 as well as FIG. 8, when the control knob 134 of themode switch (FIG. 9) is rotated counter-clockwise to the continuouslyvariable position so as to activate the middle contact of each of theswitches 81-85, the wiper arm WA is electrically connected to the sourceof negative potential B, and the control knob can be adjusted to varythe potentiometer resistance connected in the circuit with the capacitorC1 to determine the speed of the motor in the continuously variable mode'of operation, as previously described. The motor 22, of course, isconnected directly to the source of negative potential B by the switchS4, the ring r0 is electrically disconnected from the circuit and thering 23 is connected to ground through the switch S5.

When the mode switch 130 is switched to the intermittent positionwherein all of the movable contacts of the switches Sl-SS engage theextreme clockwise contact, the wiper arm WA is electrically connected tothe source of negative potential B through the conductive segment r9B.The ring r0 is connected to the source of negative potential B throughthe switch S3 and conductive seg ment r9A, and the ring r5 is groundedthrough switch S5. The capacitor C2 is added to the circuit through theswitch S1 and the conductive segment rlA, and the capacitor Q1 isconnected in the circuit during the controlled torque region by theconductive segment r1B. The speed of thernotor during the controlledtorque region is determined by theposition of the wiper arm WA whichcontrols the potentiometer resistance connected to the capacitor C1 todetermine the RC time constant in the controlled torque region.

When the wiper blades enter the region, the capacitor C1 is electricallydisconnected from the circuit and the capacitorCZ is connected to.ground during the entire 0 region by the elongated conductive segment onthe ring r3 As previously described, the capacitor C2 is charged on theupstroke withthe charge retained during the controlled torque region.The base of the transistor Q1 immediately becomes positive to turn thetransistors OFF and deenergize the motor 22 when the negative terminalof the capacitor C2 is grounded. The wiper blades will coast aspreviously described, and assuming the windshield is not wet enough tocause the dwell period to be skipped, they will come to rest at somepoint in the 0 region with the wiper contact assembly 118 on one of theconductive segments r0A-r0F.

The particular conductive segment r0A-r0F which is connected to thenegative potential -B through ring r0, switch S3 and the conductivesegment r9A determines the potentiometer resistance connected to thecapacitor C2 to control the length of the dwell period. The further thewiper blades coast into the 0 region in response to increased moistureon the windshield before stopping, the lower the value of resistanceconnected to the capacitor C2, and the shorter the dwell period which,of, course, is the desired result. When the capacitor C2 dischargessufiiciently so that the base of the transistor Q1 is no longerpositive, the transistors are turned ON to energize the motor 22 todrive the wiper blades out of the 0. region and into the full torqueregion wherein the transistors are removed from the circuit and themotor 22 is connected directly to ground through the rings r6 and r5.Thus this embodiment provides a single stop dwell period with the lengthof the dwell period automatically responsive to the moisture on thewindshield.

When the mode switch 130 is turned to the OFF position, which is theposition illustrated in FIG. 10, the control device completes one cycleof the intermittent mode of operation as already described, the motor isautomatically deenergized when the wiper contact assembly 118 leaves thering r8 and then electrodynamically braked when the wiper contactassembly enages the short conductive segment on the ring r7. Thisimmediately stops the wiper blades in the desired park position. Sincethe conductive segment on the ring 17 lies entirely within the fulltorque region, the transistors will be removed from the circuit when themode switch 130 is turned back onfor a subsequent operation so that anystall torque will be absorbed by the motor and not the transistors. Fromthe foregoing it is apparent that the printed circuit card 104 providesthe advantages discussed in connection with the embodiment of FIG. 6,including the advantage of having the 6 region lie entirely within thereturn stroke of the wiping cycle to provide the maximum reduction ofkinetic energy before reaching the short conductive segment on ring 7.

Referring to FIG. 11, the improved speed torque curves obtained by theembodiment of FIGS. 7-9 are illustrated with the speed or r.p.m. of theoutput shaft 106 of the wiper motor unit 110 plotted against the torqueon the output shaft in ounce inches. Three separate curves are shown forfull, medium and low speeds in the continuous mode of operation. Anideal speed torque curve of course would be a horizontal line, and thisideal is approached by the curves of FIG. 11 at high loads. At lightloads the curves have a greater slope which is an advantage in theintermittent mode of operation.

Referring to FIG. 13, an improved printed circuit card 260 isillustrated which is reversed relative to the card 104 of FIG. 8 forcooperating with a clockwise rotating wiper contact assembly 118. Thegaps in the rings r0 and 11 are slanted rather that being disposedradially so that the wiper contact fingers engaging these rings will notlose contact with the conductive segments on these rings when crossingthe gaps. This eliminates the possibility of the wiper contact unitstopping in the gap out of contact with a conductive segment so as torequire a dwell period before the transistors turn ON to move the wipercontact assembly out of the gap. Also very short segments 262 and 264are interposed between the conductive segments on the rings R2 and R3,respectively, and a longer segment 266 is provided on the ring r2 in the0 region all of which are made of the same material as the conductivesegments but are not electrically connected to the terminals on the base40 of the card. These added segments improve the wear resistance andlife of the card and minimize any tendency for the Wiper contact fingersto wipe insulating material over the conductive segments in a manner tointerfere with the electrical connection between the wiper contactfingers and the rings R2 and R3. Segments 268-276 are provided on ringsr9, r8, r7, r6 and 10, respectively, for the same purpose. Lines or gapsbetween the wear segments and conductive segments of 0.010 inch wide canbe readily controlled with present day printed circuit manufacturingtechniques.

Referring to FIG. 14 a modification'of the control circuit of FIG. 7 isillustrated wherein a separate potentiometer P1 is provided without tapsand separate series connected resistors R3R7 are provided for thevariable dwell period feature. This allows the various dwell periods tobe changed as desired by simply using resistors R3-R7 having thenecessary value.

While it will be apparent that the embodiment of the invention hereinisclosed are well calculated to fulfill the objects of the invention, itwill be appreciated that the invention is susceptible to midification,variation and change without departing from the proper scope or fairmeaning of the subjoined claims. For example the transistors Q1 and Q2could be changed to NPN transistors and the source of negative potentialB changed to a positive potential +B. Although two capacitors C1 and C2have been shown because of the two quite different RC time constantsinvolved, the large capacitor could be used for both. If this is donethen only a small part of the potentiometer would be used or someadditional resistors could be switched into the potentiometer so thatall variation would not occur at one end of the potentiometer. It isalso noted that additional switching functions could be added to theprinted circuit card to control various auxiliary devices such as thewindshield washer, blinking safety lights or tail lights, a windshieldheater unit or de-icer unit and so forth. In the case of the windshieldwasher control the washer unit when energized, could be interruptedbriefly to allow the blades to pass so as to reduce the amount of washerfluid which is hurled outside the wiper pattern. The washer unit couldalso be deenergized during any dwell period that might occur if thecontrol device is in the intermittent mode in the event the washer fluidsquirted on the windshield does not place the system in the safety shipmode of operation.

What is claimed is:

1. A motor speed control device comprising cyclical energizing means forenergizing a motor with a cyclical burst of power, and timing meansresponsive to said cyclical energizing means for independentlycontrolling the length of time of one phase of said cycles in a mannerto regulate the speed of said motor, said cyclical energizing meansbeing responsive to the speed of said motor to vary the frequency ofsaid cycles in proportion to the speed of said motor, said timing meansbeing activated by said cyclical energizing means at a predeterminedpoint in each cycle and thereafter providing a timing controlindependent of the speed of said motor.

2. The control device as defined in claim 1 wherein said cyclicalenergizing means pulses said motor in ON- OFF cycles with substantiallyfull power being delivered to the motor during the ON portion of eachcycle and no power during the OFF portion of each cycle, and whereinsaid timing means independently controls the length of time the motor isON during each cycle.

3. The control device as defined in claim 1 wherein said timing meansincludes means for varying the length of time of said one phase of saidcycles to vary the speed of said motor.

4. The control device as defined in claim 1 wherein said cyclicalenergizing means includes rotary switch means driven by said motor forproducing ON-OFF cycles for energizing said motor.

5. The control device as defined in claim 4 wherein said timing means isactivated each time said motor is turned OFF and wherein said timingmeans turns said motor ON after a predetermined length of time in theevent said rotary switch means is still in an OFF position.

6. The control device as defined in claim 5 wherein said motor is anelectric motor and said timing means includes transistor means forenergizing said motor when the transistor means is turned ON and RC timeconstant means responsive to said rotary switch means for controllingthe OFF time of said transistor means.

7. The control device as defined in claim 6 including means for varyingsaid RC time constant means to vary the OFF time of said transistormeans in a manner to vary the speed of said motor.

8. The control device as defined in claim 4 wherein said rotary switchmeans comprises electric insulating means having a plurality ofconductive rings thereon slidably engaged by wiper contact means, one ofsaid two last mentioned means being rotatably driven by said motor andthe other being fixed against rotation.

9. The control device as defined in claim 8 wherein said motor is anelectric motor, and including transistor means for controlling theenergization of said motor and RC time constant means for controllingthe ON-OFF time of said transistor means, and wherein said rotary switchmeans has first, second and third spaced apart rings thereon, said firstring having a substantially continuous conductive segment thereon, saidsecond and third rings having a plurality of conductive segments thereonwith non-conductive segments therebetween with the conductive segmentsof said second ring interposed between the conductive segments of thethird ring, said wiper contact means electrically interconnecting saidrings with one another, and wherein said control means includes circuitmeans for connecting said rings to said RC time constant means toalternately charge the capacitance thereof when said wiper contact meansengages the conductive segments on the second ring and discharge saidcapacitance through the resistance thereof of said RC time constantmeans when said wiper contact means engages the conductive segments onthe third ring, the charge on said capacitance determining the state ofsaid transistor means.

10. A motor speed control device comprising cyclical energizing meansfor energizing a motor in a pulsed mode of operation with high frequencypulsing cycles, and timing means responsive to said cyclical energizingmeans for providing a time dependent control over the length of time ofone phase of each of said pulsing cycles, said timing means beingactivated by said cyclical energizing means at a predetermined point ineach pulsing cycle andbeing conditioned during the next phase to prepareit for con-' trolling the length of time of said one phase ofthe nextcycle. I 11. The invention as defined in claim 10 wherein said timingmeans can be varied to vary said predetermined time interval.

12. The invention as defined in claim 10 wherein said timing means isactivated at the beginning of said one phase of each cycle. 1

13. The invention as defined in claim '12 wherein said pulsing cyclescomprise ON-OFF cycles having an ON phase and an OFF phase. i

14. The invention as defined in claim 13 wherein said one phase is theOFF phase, and said timing means terminates said OFF phase by initiatingthe ON phase in the event said cyclical energizing means has notpreviously initiated said ON phase.

15. The invention as defined in claim 14 wherein said timing means isconditioned during the ON phase of each cycle.

16. The invention as defined in claim 10 including means for varying thefrequency of said cyclical energizing means in response to the speed ofthe motor. 7

17. The invention as defined in claim 10 wherein said cyclicalenergizing means is driven by the motor output shaft so that thefrequency thereof varies directly with the speed of the motor.

References Cited UNITED STATES PATENTS ORIS L. RADER, Primary ExaminerH. HUBERFELD, Assistant Examiner v US. or. X.R. 15 250.12, 250.17; 31s444, 447, 466

9/1967 Wood l5.250.12-

